The present invention relates to a circuit for correcting the printing dot positions of a printer apparatus which produces printed material by means of a head having a plurality of on-demand type ink jet spray nozzles.
In a conventional printer having a head including a plurality of ink jet nozzles so arranged on the head that they are separated from one another in the direction of head scanning, a correction method of this kind uses a shift register, or the like. In such a method, it is clear that the correction can be made in dot pitch unit steps only, and steps of separating distances are required, which is not efficient. Also, there is a method that delays the printing timing of the nozzle which is trailing to the scanning direction of the head for a time corresponding to the separating distance thereof. This method has the drawback that the relationship between the distance and the time must be maintained extremely precise. When it is considered in combination with the trend toward miniaturization which reduces the dot pitch, the maintenance of the constant speed property of the head scanning requires extremely high costs.
Although the technical development of the multinozzle is in progress in correspondence to the market request for high densification, high speed printing, and colored printing, a structure constituting a plurality of nozzles united in one body in a plane in a designated high density pitch has not yet been developed, and the present technology is at a point where a head is formed by combining a number of heads. Therefore, in order to counteract manufacturing inaccuracies, it is necessary to correct arbitrary nozzle intervals. When the conventional technology is considered in view of the point described above, it is deficient with regard to flexibility of the correction length, and since its greatest weakness is that the reference is reversed in dependence to the scanning direction of the head, it is difficult to have dots formed during forward movement and dots formed during return movement formed in a line, although correction could be made for each direction of movement and, in the actual case, the printing is limited in one direction only, so that the printing time becomes long.
The present invention intends to overcome the weak points of the conventional technology and to provide a correcting method having high precision, and to realize an apparatus having high printing quality.